The present invention relates to a method for replacing a signal controlling an actuator in a remote-controlled flying device with another signal. Said actuator may be a motor, a stabilizing system, a camera rack, a camera as such, the legs of the device, or another radio controlled actuator.
Uses of the invention include, for example, miniature helicopters, multicopters and airplanes. As it is well known, the above mentioned actuators of these devices are radio controlled in such a way that their power, position, and other functions may be adjusted by remote control. For example, the power to be input in an electric motor may be controlled by transmitting a signal at a given wavelength from a radio transmitter over a given channel to the receiver of the flying device, which forwards it to a flight control device, such as e.g. a computer, from which it is transferred by a pulse width modulation technique, a bus technique, or another known technique to an electronic speed controller controlling the motor, or to a servo unit controlling a mechanical speed controller, and the speed controller adjusts the power to be supplied by a power source, such as e.g. an accumulator or a battery, to the motor, to a given level corresponding to a given signal.
In a fault situation, it may be necessary to deploy the parachute of the flying device to avoid a danger being caused by the device when falling onto the ground, and in connection with deploying the parachute, the motor(s) of the device also have to be switched off for safety reasons. One application of the invention relates to this particular situation.
When for example a multicopter is placed in such a situation, it is common practice to switch off the motors of the rotors after deploying the parachute, by transmitting a radio signal from the ground to modify the signal in such a way that the speed controllers stop the power supply to the motors. It is known that the parachute may be deployed either by remote control or automatically by a control unit for the parachute in the device. In the latter case, the deploying may be based on the use of e.g. an acceleration sensor, a position transmitter, or a pressure-sensitive gauge.
This known technology has the disadvantage that there is often a delay between the deployment of the parachute and the switching off of the motors. Particularly when the parachute is automatically deployed by the control unit, this delay is unavoidable. This delay, in turn, may cause further problems, for example in such a way that uncontrolled movements of the device result in the destruction of the parachute if it comes into contact with the rotor blades.
Other actuators mentioned further above, such as the camera rack, the camera itself, or the legs of the device, are controlled, according to the prior art, in such a way that for changing their position, a radio signal corresponding to this change is transmitted by a remote controller, transferred from the receiver via the flight control device to the servo unit controlling the actuator by a known signalling technique (e.g. PWM, PPM) or by a bus technique.
It is known that all the channels of the radio controller are constantly updated during the operation of the flying device, and a signal is then constantly provided for the actuators. For a given period of time, the signal may also be constant, whereby e.g. the power of the motor remains constant for that time. The pulse length of the PWM signal may typically vary, for example, between 1.0 and 2.0 ms, whereby when the motor is running at half capacity, a signal with a constant pulse length of 1.5 ms is input in the speed controller. In a corresponding way, the servo units for the actuators may be set to operate in such a way that the signal pulse lengths corresponding to their extreme values are 1.0 ms and 2.0 ms when operating in said pulse length range.
The most serious drawback of this technique of prior art is the fact that position changes of the actuators are dependent on the reactions of the user of the flying device, whereby e.g. the turning of the legs of the device to the landing position may be delayed in an abnormal situation.